1. Field
The present invention relates to a laser beam irradiation apparatus and a substrate sealing method.
2. Description of the Related Art
Recently, portable thin-type flat display devices are increasingly being used. An electroluminescence display device, which is among the flat display devices, is a self-emissive type display device which has a wide view angle, an excellent contrast, and a quick response speed, and thus, the electroluminescence display device has attracted attention as a next-generation display device. In addition, an organic light-emitting display device in which a light-emitting layer is formed of an organic material has better characteristics in brightness, a driving voltage, and a response speed and may be polychromized when compared with a non-organic light-emitting display device.
A typical organic light-emitting display device has a structure in which at least one organic layer including a light-emitting layer is interposed between a pair of electrodes.
According to such an organic light-emitting display device, when moisture or oxygen enters into the inside from a surrounding environment, due to oxidization, exfoliation, or the like of an electrode material, the life span of an organic light-emitting device (OLED) is reduced, light-emitting efficiency is lowered, a light-emitting color is deteriorated, and other problems may occur.
Thus, when organic light-emitting display devices are manufactured, a process of sealing an OLED to prevent moisture from permeating by separating the OLED from the outside is typically performed. As a sealing method, a method of laminating a non-organic thin film and an organic polymer, such as polyester (PET), on a second electrode of an organic light-emitting display device, or a method of forming a moisture absorption material inside an encapsulation substrate, charging a nitrogen gas inside the encapsulation substrate, and sealing an edge of the encapsulation substrate with a sealant, such as epoxy, is usually used.
However, these methods cannot perfectly block OLED destructive factors, such as moisture, oxygen, or the like, introduced from the outside, and thus, it is disadvantageous to apply these methods to an organic light-emitting display device that is especially vulnerable to moisture. Furthermore, processes for realizing these methods are also complicated. To address the problems described above, a substrate sealing method for improving adhesivity between an OLED substrate and an encapsulation substrate by using a frit as a sealant has been proposed.
In this case, since perfect sealing between the OLED substrate and the encapsulation substrate is achieved by using a structure of sealing an organic light-emitting display device by coating a frit on a glass substrate, the organic light-emitting display device may be more effectively protected.
According to a method of sealing a substrate with a frit, the substrate is sealed by coating the frit on a sealing part of each organic light-emitting display device and irradiating a laser beam on the sealing part of each organic light-emitting display device while moving a laser beam irradiation apparatus to harden the frit.